Hall effect devices are semiconductor devices used to measure magnetic field. They produce an output signal proportional to magnetic field. At zero magnetic field, they tend to output a signal, which is usually different from zero: this is their offset error (=zero field error).
Hall effect devices comprise a Hall effect region where the Hall effect takes place and with three or more contacts in or in ohmic contact with the Hall effect region. An electrical contact to the Hall effect region can be made by a contact diffusion or implantation process, for example. Sometimes several contacts can be connected via metal lines (in the interconnect layer of the semiconductor technology) to the same terminal. Terminals can be used to supply the device with electric power and to tap its output signals.
If the Hall effect region is a two-dimensional electron gas (2DEG), it can be regarded as a sheet layer with vanishing thickness (in practice the thickness can be in the order of 10 nm) and contacts can be made differently than with tubs (because of the thin device). Note that 2DEG is an electron gas that is free to move in two dimensions, but tightly confined in the third.
Hall plates, which we also call Horizontal Hall effect devices or HHalls, are flat devices with thicknesses 5 . . . infinitely (typically 50) times smaller than their lateral size. They are used to detect magnetic field components along their thickness direction (i.e. direction into the semiconductor substrate). In silicon technology Hall plates are currently typically 1 . . . 3 μm thick and 10 . . . 100 μm large in lateral directions. Their layout can be rectangular, square, circular, octagonal, cross-shaped, or even triangular.
Vertical Hall effect devices or VHalls are stout devices where one lateral dimension is comparable (0.2 times up to 10 times) to their thickness direction (i.e. direction into the semiconductor substrate). They often have the shape of long stripes, mostly straight, sometimes curved, arc-shaped, or even circular rings. They can be used to detect magnetic field components parallel to the semiconductor main surface.
The terms “horizontal” and “vertical” denote the orientation of the plate-like geometry of the devices with respect to the main surface of the semiconductor die.
As mentioned before, Hall effect devices can suffer from offset error. Offset error is the presence of an output signal in the absence of some input quantity. For Hall sensors, the offset error would be an output signal indicative of an input magnetic field when in fact no magnetic field is present.
Offset error can relate to different causes, two of which are raw offset error and residual offset error. Raw offset error can refer to an offset error present in a particular operating phase. Residual offset error can refer to an offset error present in an overall or total output signal, such as a signal which is a combination of those from individual operating phases.
One approach for reducing or eliminating offset error is using a multi-contact Hall sensor. Three-contact or four-contact HHalls or VHalls can be operated in a spinning current-type mode, which changes the supply or sense role of the contacts in multiple clock phases such that any offset is reduced when the signals from the multiple clock phases are combined. Even so, the residual offset error can remain higher than desired, such as in the range of about 1 milli-Tesla (mT).
Both conventional HHalls and VHalls are limited with respect to detecting magnetic field components in the 3-dimensional (3D) space. It is therefore desirable to have Hall sensor devices with large magnetic sensitivity to specific magnetic field components in 3D-space. It is further desirable to combine signals tapped in different operating modes in a favorable way to cancel out offset errors and still preserve a large 3D magnetic sensitivity.